JP2014074650A - Inspection equipment for optical element and inspection method for optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To directly and speedily inspect optical characteristics of an optical element in which two types of polar screens with polarization directions perpendicular to each other are two-dimensionally arranged.SOLUTION: An inspection method is for a mixed type filter 10 in which a first polarization region for transmitting a first polarization component of incident light and a second polarization region for transmitting a second polarization component of the incident light are two-dimensionally arranged. An angle of an analyzer 123 arranged on a subsequent stage of the mixed type filter is set as 45 degrees. According to a transmission light intensity of inspection light detected while rotating a polarizer 117 arranged on a preceding stage of the mixed type filter by every predetermined angle, a TM transmission rate and a TE transmission rate of the mixed type filter are calculated.

Description

  The present invention relates to an optical element inspection apparatus and an optical element inspection method, and more particularly, to an optical element capable of determining optical characteristics of an optical element in which polarization regions having orthogonal polarization directions are two-dimensionally arranged at high speed and with high accuracy. The present invention relates to an inspection apparatus and an optical element inspection method.

With the progress of semiconductor microfabrication technology, it has become possible to produce polarizing filters having different optical characteristics in unit regions each having a side of about several μm, and their use is progressing.
For example, in a liquid crystal panel or the like, a color filter array in which RGB filters are respectively produced in unit areas each having a side of about several μm by using photolithography in which a color resist mixed with a dye is applied to a substrate and then exposed and developed. Has been put to practical use.
In addition, a polarizing filter (hereinafter referred to as a “mixed filter”) in which a sub-wavelength polarizing element, a wire grid polarizer, or a photonic crystal element having a microstructure with a length equal to or shorter than an incident wavelength is manufactured in a unit region having a side of about several μm. ") Has been put to practical use. In the mixed filter, regions (filters) having different polarization characteristics are two-dimensionally arranged.
Incidentally, the inspection of the optical characteristics of the polarizing filter is generally performed by irradiating the optical element to be inspected with inspection light and measuring the reflection intensity and transmission intensity of the inspection light (see, for example, Patent Document 1).

However, it is difficult to inspect the optical characteristics of the mixed filter with the conventional inspection method for optical elements as described in Patent Document 1. That is, since the unit area of the mixed filter is about several μm on a side, when the inspection light is irradiated from a general optical characteristic evaluation apparatus, the size of the unit area is larger than the size of the area irradiated with the inspection light. Therefore, there is a problem that the transmittance, reflectance, etc. cannot be measured for each unit region of the mixed filter.
Conventionally, as an alternative, a monitor pattern (or a monitor sample) having a size that can be measured by a general optical characteristic evaluation apparatus, in other words, a size sufficiently larger than the size of an area irradiated with inspection light has been used. . In other words, an optical filter is manufactured under the same conditions as the filter formed in each unit area of the mixed filter, the optical characteristics of the monitor pattern are evaluated, and the evaluation result is applied to the mixed filter, whereby the mixed filter The optical properties of were evaluated.

However, mixed filters using fine structures such as photonic crystals and wire grid polarizers may have different dimensions after processing due to the difference in the fine structure arrangement between the mixed filter and the monitor pattern. There is. As a result, the optical characteristics of the polarizing filter on the mixed filter may not match the optical characteristics of the monitor pattern.
In addition, when shipping mixed filters as products, it is necessary to inspect optical characteristics unevenness and defects, but these cannot be replaced by monitor patterns, and actual mixed filters must be inspected directly. There is.

Therefore, an optical element inspection apparatus and inspection method that can inspect optical characteristics of a mixed filter at high speed and evaluate the quality of the optical element with high accuracy without substituting a monitor pattern have been desired.
The present invention has been made in view of the above circumstances, and directly and rapidly inspects the optical characteristics of an optical element in which two types of polarizing filters whose polarization directions are orthogonal to each other are two-dimensionally arranged. An object of the present invention is to provide an optical element inspection device and an optical element inspection method that can be evaluated with high accuracy.

  In order to solve the above problems, the invention according to claim 1 is characterized in that a first polarization region that transmits a first polarization component of incident light and a first polarization component of the incident light that is orthogonal to the first polarization component. An inspection device for an optical element in which a second polarization region that transmits a second polarization component is two-dimensionally arranged, and is a region that is sufficiently larger than the first polarization region and the second polarization region of the optical element A light source for irradiating the inspection light with respect to the optical element, two inspection polarizers that are respectively disposed in a front stage and a rear stage of the optical element and transmit a predetermined polarization component of the inspection light, and the two inspection lights Among the polarizers, the inspection polarization holding the one inspection polarizer so that the transmission axis of one inspection polarizer is an angle rotated by 45 degrees from the angle of the transmission axis of the first polarizing region. A second holding detector and the other of the two inspection polarizers. Inspection polarizer rotating means for rotating the transmission axis of the polarizer for every predetermined angle, transmitted light intensity for detecting the transmitted light intensity of the inspection light transmitted through the two inspection polarizers and the optical element The inspection light transmitted through the other inspection polarizer rotated at a predetermined angle by the detection means and the inspection polarizer rotation means is detected by the transmitted light intensity detection means, and the detected predetermined Transmittance calculating means for calculating the TM transmittance and the TE transmittance of the optical element based on the transmitted light intensity for each angle is provided.

In the present invention, inspection polarizers are arranged in the front and rear stages of the optical element, respectively, and the angle of one of the inspection polarizers is set to an angle rotated by 45 ° with respect to the transmission axis angle of the first polarizing region. The transmitted light intensity is measured while rotating the other inspection polarizer at every predetermined angle. The transmitted light intensity obtained by the measurement changes depending on the transmission axis angle of the other inspection polarizer.
According to the present invention, the TM transmittance and the TE transmittance of the optical element are calculated based on the transmitted light intensity that changes depending on the transmission axis angle of the other inspection polarizer. It is possible to directly inspect the optical characteristics of the optical element in which the one polarization region and the second polarization region are two-dimensionally arranged at high speed, and to evaluate the quality of the optical element with high accuracy.

(A)-(c) is a schematic diagram of the optical element by which the wire grid polarizer is arrange | positioned. It is a schematic diagram for demonstrating the principle of this invention. It is a schematic structure figure of an inspection device concerning one embodiment of the present invention. It is the flowchart which showed the calculation method of the optical characteristic of the optical element performed by a test | inspection apparatus. (A), (b) is the schematic diagram which showed an example of the optical element which can be made into a test object in this invention. It is the graph which showed the change of the transmittance | permeability when the angle of the transmission axis of an analyzer is 0 degree. It is the graph which showed the change of the transmittance | permeability when the angle of the transmission axis of an analyzer is 45 degrees. It is the graph which showed the change of the transmittance | permeability when the angle of the transmission axis of an analyzer is 90 degrees. FIG. 10 is a schematic diagram of an optical element that is an inspection target in the fourth embodiment.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the components, types, combinations, shapes, relative arrangements, and the like described in this embodiment are merely illustrative examples and not intended to limit the scope of the present invention only unless otherwise specified. .

[Optical element to be measured]
1A to 1C are schematic views of an optical element in which a wire grid polarizer is arranged.
A wire grid polarizer is an optical element in which fine metal lines (metal wires) are periodically arranged in parallel in one direction. When the distance (pitch) between the metal lines is sufficiently smaller than the wavelength of the incident light, light having an electric field component that vibrates in a direction parallel to the direction in which the metal lines extend (line direction) is reflected, and the metal lines extend. It has an optical characteristic of transmitting an electric field component that vibrates in a direction perpendicular to the direction.

  Hereinafter, TE polarized light (S polarized light) of a wire grid polarizer is polarized light having an electric field component that vibrates in parallel with a metal line forming the wire grid, and TM polarized light (P polarized light) is a wire. It is defined as polarized light having an electric field component that vibrates perpendicularly to the metal lines forming the grid.

First, as shown in FIGS. 1A and 1B, a wire grid polarizer composed of a single polarization region is considered.
As shown in FIG. 1A, in a wire grid (X-direction wire grid) in which a metal line structure in which fine metal lines are arranged in parallel in the X direction with respect to the entire region of the wire grid polarizer is formed. The TM polarized light (P polarized light) transmittance is defined as t _TM1 and the TE polarized light (S polarized light) transmittance is defined as t _TE1 . Similarly, as shown in FIG. 1B, a wire grid (Y-direction wire grid) in which a metal line structure is formed in which fine metal lines are arranged in parallel in the Y direction with respect to the entire region of the wire grid polarizer. ) Also defines the TM polarized light (P polarized light) transmittance as t _TM2 and the TE polarized light (S polarized light) transmittance as t _TE2 .

The transmittance t is defined as a value derived from the following equation.
Transmittance t = [(light intensity with sample)] / [(light intensity without sample)]
Here, “light intensity with sample” means that a sample (wire grid) is placed on the optical path of inspection light between a light source and a detector (light receiving element) that detects the intensity of inspection light emitted from the light source. This is the light intensity of the inspection light detected by the detector when a polarizer is disposed. “Light intensity without sample” means inspection light detected by the detector when no sample (wire grid polarizer) is placed on the optical path of the inspection light between the light source and the detector. It is the light intensity.
The polarization selection performance of the wire grid polarizer is expressed by its extinction ratio (contrast), that is, “(TM transmittance) / (TE transmittance)”. The higher these values, the better the polarization selection performance, ie, the wire grid. This indicates that there are few defects.

  Next, consider an optical element in which a plurality of regions having different polarization characteristics are mixed as shown in FIG. The illustrated mixed filter 10 has a plurality of fine unit regions 11 (11x, 11y) divided into micron-order regions, and each unit region 11 has an X-direction wire grid 11x or a Y-direction. A wire grid 11y is formed. That is, in the mixed filter 10, an X-direction wire grid 11x (first polarization region) that transmits light (0 ° polarization: first polarization component) having an electric field component oscillating in the X direction out of the incident light. And a Y-direction wire grid 11y (second polarization region) that transmits light having an electric field component oscillating in the Y direction (90 ° polarization: second deflection component) are two-dimensionally arranged at a predetermined area ratio. ing. The mixed filter 10 includes two types of wire grids in which the directions of the metal lines are orthogonal to each other.

[Outline of the Invention]
An outline of the characteristics and procedure of the method for evaluating the optical characteristics of the mixed filter 10 according to the present invention will be described. FIG. 2 is a schematic diagram for explaining the principle of the present invention. As shown in FIG. 2, a polarizer 117, a mixed filter 10 as a measurement target sample, and an analyzer 123 are sequentially arranged on the optical path of the inspection light. Here, with respect to the X-direction wire grid 11x and the Y-direction wire grid 11y of the mixed filter 10, the angles of the transmission axes thereof are adjusted to the X axis (0 °) and the Y axis (90 °), respectively.
[Procedure 1-1] The transmission axis of the analyzer 123 is set to be fixed to the x axis (x component transmission), and the intensity of the inspection light transmitted through the analyzer 123 is detected and detected while the polarizer 117 is rotated (φdeg). The optical characteristics of the mixed filter 10 are acquired from the intensity of the inspection light thus obtained.
[Procedure 1-2] The transmission axis of the analyzer 123 is set to be fixed to the y-axis (y component transmission), and the intensity of the inspection light transmitted through the analyzer 123 is detected while rotating the polarizer 117 (φdeg). The optical characteristics of the mixed filter 10 are acquired from the intensity of the inspection light thus obtained.
[Procedure 2] The transmission axis of the analyzer 123 is set to 45 deg fixed (45 deg component transmission), and the intensity of the inspection light passing through the analyzer 123 is detected while rotating the polarizer 117 (φ deg), and the detected inspection is detected. The optical characteristics of the mixed filter 10 are acquired from the light intensity.

Procedure 1-1 is a state where the angle of the transmission axis of the analyzer 123 is matched with the angle of one transmission axis of the wire grid constituting the mixed filter 10 (here, the X-direction wire grid 11x). This is a step of acquiring ten optical characteristics. By performing the procedure 1-1, the TM transmittance t _TM1 of the X-direction wire grid 11x can be obtained.
Procedure 1-2 is performed in a state where the angle of the transmission axis of the analyzer 123 is matched with the angle of the other transmission axis of the wire grid constituting the mixed filter 10 (here, the Y-direction wire grid 11y). This is a step of acquiring optical characteristics of the mold filter 10. By performing the procedure 1-2, the TM transmittance t _TM2 of the Y-direction wire grid 11y can be obtained.

Further, in step 2, the optical characteristics of the mixed filter 10 are adjusted in a state where the angle of the transmission axis of the analyzer 123 is adjusted to an intermediate angle between the transmission axes of the two wire grids constituting the mixed filter 10. It is a process to acquire. That is, in this step, the optical characteristic is acquired by setting the angle of the transmission axis of the analyzer 123 to 45 ° or 135 °. By performing the procedure 2, the TM transmittance t _TM and the TE transmittance t _TE as the entire mixed filter 10 can be obtained.
Here, the TM transmittance of the mixed filter 10 as a whole is the sum of the TM transmittance of the X-direction wire grid and the TM transmittance of the Y-direction wire grid. The TE transmittance of the mixed filter 10 as a whole is the sum of the TE transmittance of the X direction wire grid and the TE transmittance of the Y direction wire grid. Further, the extinction ratio = (TM transmittance t _TM ) / (TE transmittance t _TE ) of the mixed filter 10 as a whole can be obtained from the obtained TM transmittance t _TM and TE transmittance t _TE .

[Jones calculation method]
The Jones calculation method (Jones vector) necessary for illustrating the principle of the present invention will be described below with reference to FIG. As shown in the figure, the inspection light passes through the polarizer 117, the mixed filter 10 (measurement target), and the analyzer 123 in this order. The mixed filter 10 to be measured is shown in FIG. Hereinafter, for convenience of explanation, the interference term of the inspection light transmitted through the X-direction wire grid 11x and the Y-direction wire grid 11y of the mixed filter 10 is ignored.

にて与えられる。
混在型フィルタ１０のＸ方向ワイヤグリッド１１ｘに関するジョーンズマトリクスは、

にて与えられる。
混在型フィルタ１０のＹ方向ワイヤグリッド１１ｙに関するジョーンズマトリクスは、

にて与えられる。
従って、偏光子１１７及び混在型フィルタ１０のＸ方向ワイヤグリッド１１ｘを透過した検査光の電場ベクトル（Ｅ′１，ｘ，Ｅ′１，y）は、偏光子１１７を透過した検査光の電場ベクトルを用いて、

と表せる。 When the electric field vector of the inspection light transmitted through the polarizer 117 (transmission axis φ) is Ex and the y component is Ey,

Given in
The Jones matrix for the X-direction wire grid 11x of the mixed filter 10 is

Given in
The Jones matrix for the Y-direction wire grid 11y of the mixed filter 10 is

Given in
Therefore, the electric field vector (E′1, x, E′1, y) of the inspection light transmitted through the polarizer 117 and the X-direction wire grid 11x of the mixed filter 10 is the electric field vector of the inspection light transmitted through the polarizer 117. Using,

It can be expressed.

と表せる。
また、透過軸がθである場合の検光子１２３のジョーンズマトリクスＪ（θ）は、回転行列Ｒ（θ）を用いて、

・・・式（１）
と表せる。ただし、

従って、偏光子１１７（透過軸θ）、混在型フィルタ１０のＸ方向ワイヤグリッド１１ｘ、及び検光子１２３を透過した検査光の電場ベクトル（Ｅ″１，ｘ，Ｅ″１，y）は、

・・・式（２）
と表せる。
また、偏光子１１７、混在型フィルタ１０のＹ方向ワイヤグリッド１１ｙ、及び検光子１２３を透過した検査光の電場ベクトル（Ｅ″２，ｘ，Ｅ″２，y）は、

・・・式（３）
と表せる。 Further, the electric field vector (E′2, x, E′2, y) of the inspection light transmitted through the polarizer 117 and the Y-direction wire grid 11y of the mixed filter 10 is the electric field vector of the inspection light transmitted through the polarizer 117. Using,

It can be expressed.
Further, the Jones matrix J (θ) of the analyzer 123 when the transmission axis is θ is obtained by using the rotation matrix R (θ),

... Formula (1)
It can be expressed. However,

Therefore, the electric field vector (E ″ 1, x, E ″ 1, y) of the inspection light transmitted through the polarizer 117 (transmission axis θ), the X-direction wire grid 11x of the mixed filter 10 and the analyzer 123 is

... Formula (2)
It can be expressed.
The electric field vector (E ″ 2, x, E ″ 2, y) of the inspection light transmitted through the polarizer 117, the Y-direction wire grid 11y of the mixed filter 10 and the analyzer 123 is

... Formula (3)
It can be expressed.

であるから、偏光子１１７（透過軸０°）、混在型フィルタ１０のＸ方向ワイヤグリッド１１ｘ、及び検光子１２３を透過した検査光の電場ベクトルは、式（２）より、

にて与えられる。同様に、偏光子１１７（透過軸０°）、混在型フィルタ１０のＹ方向ワイヤグリッド１１ｙ、及び検光子１２３を透過した検査光の電場ベクトルは、式（３）より、

にて与えられる。 [Principle of the present invention: Procedure 1-1: Measurement with an analyzer angle of 0 °]
First, the case where the angle of the transmission axis of the analyzer 123 is fixed to the x-axis (0 °) will be described.
The Jones matrix J (0 °) of the analyzer 123 when the angle of the transmission axis is 0 ° is obtained from the equation (1).

Therefore, the electric field vector of the inspection light transmitted through the polarizer 117 (transmission axis 0 °), the X-direction wire grid 11x of the mixed filter 10 and the analyzer 123 is obtained from the equation (2):

Given in Similarly, the electric field vector of the inspection light transmitted through the polarizer 117 (transmission axis 0 °), the Y-direction wire grid 11y of the mixed filter 10 and the analyzer 123 is expressed by the following equation (3):

Given in

にて与えられ、偏光子１１７、混在型フィルタ１０のＹ方向ワイヤグリッド１１ｙ、及び検光子１２３を透過した検査光の強度Ｉ２は、

にて与えられるから、検光子１２３を透過した検査光の強度Ｉは、

にて与えられる。ここで混在型フィルタ１０のＸ方向ワイヤグリッド１１ｘとＹ方向ワイヤグリッド１１ｙの作製精度が同一であると仮定する。即ち、ｔ_ＴＥ２＝ｔ_ＴＥ１と仮定する。Ｘ方向ワイヤグリッドの偏光選択性能が高く「ｔ_ＴＭ１＞＞ｔ_ＴＥ１」であるとき、

と近似できるから、検光子１２３を透過した検査光の強度Ｉは、近似的には

となる。即ち、偏光子１１７の透過軸φを変化させながら検光子１２３を透過した検査光の強度Ｉを検出すれば、得られた測定値のサインカーブの振動中心又は振幅が（１／２）（ｔ^２ _ＴＭ１）となるので、Ｘ方向ワイヤグリッドのＴＭ透過率ｔ_ＴＭ１を得ることができる。
なお、偏光子１１７の透過軸φを角度９０°にした時に検光子１２３を透過した検査光の強度Ｉを測定し、その値からＴＭ透過率ｔ_ＴＭ１を得ることもできる。 Here, the intensity I1 of the inspection light transmitted through the polarizer 117, the X-direction wire grid 11x of the mixed filter 10, and the analyzer 123 is

The intensity I2 of the inspection light transmitted through the polarizer 117, the Y-direction wire grid 11y of the mixed filter 10 and the analyzer 123 is given by

Therefore, the intensity I of the inspection light transmitted through the analyzer 123 is

Given in Here, it is assumed that the production accuracy of the X-direction wire grid 11x and the Y-direction wire grid 11y of the mixed filter 10 is the same. That is, it is assumed that t _TE2 = t _TE1 . When the polarization selection performance of the X-direction wire grid is high and “t _TM1 >> t _TE1 ”,

Therefore, the intensity I of the inspection light transmitted through the analyzer 123 is approximately

It becomes. That is, if the intensity I of the inspection light transmitted through the analyzer 123 is detected while changing the transmission axis φ of the polarizer 117, the vibration center or amplitude of the sine curve of the obtained measurement value is (1/2) (t ² _TM1 ), the TM transmittance t _TM1 of the X-direction wire grid can be obtained.
It is also possible to measure the intensity I of the inspection light transmitted through the analyzer 123 when the transmission axis φ of the polarizer 117 is set to an angle of 90 °, and obtain the TM transmittance t _TM1 from the measured value.

にて与えられる。ここで混在型フィルタ１０のＸ方向ワイヤグリッド１１ｘとＹ方向ワイヤグリッド１１ｙの作製精度が同一であると仮定する。即ち、ｔ_ＴＥ１＝ｔ_ＴＥ２と仮定する。Ｙ方向ワイヤグリッドの偏光選択性能が高く「ｔ_ＴＭ２＞＞ｔ_ＴＥ２」であるとき、検光子１２３を透過した検査光の強度Ｉは、近似的に

となる。即ち、偏光子１１７の透過軸φを変化させながら検光子１２３を透過した検査光の強度Ｉを検出すれば、得られた測定値のサインカーブの振動中心又は振幅が（１／２）（ｔ^２ _ＴＭ２）となるので、Ｙ方向ワイヤグリッドのＴＭ透過率ｔ_ＴＭ２を得ることができる。 [Principle of the present invention: Procedure 1-2: Measurement with an analyzer angle of 90 °]
Since the procedure when the analyzer angle is 90 ° is the same as that of the procedure 1-1 except that the Jones matrix J (90 °) of the analyzer 123 is different, the description is simplified. The intensity I of the inspection light transmitted through the analyzer 123 is

Given in Here, it is assumed that the production accuracy of the X-direction wire grid 11x and the Y-direction wire grid 11y of the mixed filter 10 is the same. That is, it is assumed that t _TE1 = t _TE2 . When the polarization selection performance of the Y-direction wire grid is high and “t _TM2 >> t _TE2 ”, the intensity I of the inspection light transmitted through the analyzer 123 is approximately

It becomes. That is, if the intensity I of the inspection light transmitted through the analyzer 123 is detected while changing the transmission axis φ of the polarizer 117, the vibration center or amplitude of the sine curve of the obtained measurement value is (1/2) (t ² _TM2 ), the TM transmittance t _TM2 of the Y-direction wire grid can be obtained.

It is also possible to measure the intensity I of the inspection light transmitted through the analyzer 123 when the transmission axis φ of the polarizer 117 is set to an angle of 90 °, and obtain the TM transmittance t _TM2 from the measured value.
Furthermore, manufacturing accuracy same X-direction wire grid 11x and Y-direction wire grid 11y of mixed-filter 10, that _is, when it is assumed that _{t TM1 = t TM2 = t TM} , t TE1 = t TE2 = t TE is If one of the measurement with the transmission axis angle of the analyzer 123 set to 0 ° or the measurement with the transmission axis angle of the analyzer 123 set to 90 ° is performed, the TM of each of the X-direction wire grid 11x and the Y-direction wire grid 11y is measured. Transmittance can be obtained.

であるから、偏光子１１７（透過軸４５°）、混在型フィルタ１０のＸ方向ワイヤグリッド１１ｘ、及び検光子１２３を透過した検査光の電場ベクトルは、式（２）より、

にて与えられる。同様に、偏光子１１７（透過軸４５°）、混在型フィルタ１０のＹ方向ワイヤグリッド１１ｙ、及び検光子１２３を透過した検査光の電場ベクトルは、式（３）より、

にて与えられる。 [Principle of the present invention: Procedure 2: Measurement with an analyzer angle of 45 °]
Next, the case where the angle of the transmission axis of the analyzer 123 is fixed at 45 ° will be described. However, in the following description, for convenience, it is assumed that the production accuracy of the X-direction wire grid 11x and the Y-direction wire grid 11y of the mixed filter 10 is the same. That is, it is assumed that t _TM1 = t _TM2 = t _TM and t _TE1 = t _TE2 = t _TE .
The Jones matrix J (45 °) of the analyzer 123 when the angle of the transmission axis is 45 ° is obtained from the equation (1).

Therefore, the electric field vector of the inspection light transmitted through the polarizer 117 (transmission axis 45 °), the X-direction wire grid 11x of the mixed filter 10 and the analyzer 123 is expressed by the following equation (2):

Given in Similarly, the electric field vector of the inspection light transmitted through the polarizer 117 (transmission axis 45 °), the Y-direction wire grid 11y of the mixed filter 10 and the analyzer 123 is expressed by the following equation (3):

Given in

にて与えられ、偏光子１１７、混在型フィルタ１０のＹ方向ワイヤグリッド１１ｙ、及び検光子１２３を透過した検査光の強度Ｉ２は、

にて与えられるから、検光子１２３を透過した検査光の強度Ｉは、

・・・式（４）
と表せる。ただし、

・・・式（５） Here, the intensity I1 of the inspection light transmitted through the polarizer 117, the X-direction wire grid 11x of the mixed filter 10, and the analyzer 123 is

The intensity I2 of the inspection light transmitted through the polarizer 117, the Y-direction wire grid 11y of the mixed filter 10 and the analyzer 123 is given by

Therefore, the intensity I of the inspection light transmitted through the analyzer 123 is

... Formula (4)
It can be expressed. However,

... Formula (5)

また、原理的には、ＴＭ透過率ｔ_ＴＭとＴＥ透過率ｔ_ＴＥに、夫々混在型フィルタ１０に対するＸ方向ワイヤグリッド１１ｘの面積率、又は混在型フィルタ１０に対するＹ方向ワイヤグリッド１１ｙの面積率を乗ずることで、Ｘ方向ワイヤグリッド１１ｘとＹ方向ワイヤグリッド１１ｙのそれぞれのＴＭ透過率、及びＴＥ透過率を算出することができる。 Here, X is a DC component (a component that does not vibrate), and Y is an AC component (vibration component: coefficient of sin 2φ). When the intensity I of the inspection light transmitted through the analyzer 123 is detected while changing the transmission axis φ of the polarizer 117, the measured value of the intensity I becomes a sine curve, and in this sine curve, X appears as the vibration center, Y appears as an amplitude. Therefore, X and Y can be specifically obtained by approximating the sine curve of the measured value by the least square method or the like.
Also, if X and Y can be obtained specifically, t ² _TM , t ² _TE , t ² _TM / t ² _TE can be obtained as follows by solving the simultaneous equations of Equation (5). , TM transmittance t _TM , TE transmittance t _TE , and extinction ratio t _TM / t _TE can be obtained.

Further, in principle, the area ratio of the X-direction wire grid 11x with respect to the mixed filter 10 or the area ratio of the Y-direction wire grid 11y with respect to the mixed filter 10 is set in the TM transmittance t _TM and the TE transmittance t _TE , respectively. By multiplying, the TM transmittance and the TE transmittance of each of the X-direction wire grid 11x and the Y-direction wire grid 11y can be calculated.

As described above, in the present invention, even in a mixed filter composed of two orthogonal wire grids, the analyzer angle is set to a specific angle (0 °, 45 °, 90 °) By measuring the transmittance by rotating the element, values such as TM transmittance, TE transmittance, and approximate extinction ratio can be obtained.
In the explanation of the principle of the invention, the angle of the transmission axis of the analyzer is fixed and the angle of the transmission axis of the polarizer is changed. However, the angle of the transmission axis of the polarizer is fixed and the transmission axis of the analyzer is changed. The angle may be changed.

[Quality determination based on optical characteristics obtained by the present invention]
The quality of the mixed filter can be determined based on the optical characteristics of the mixed filter obtained by using the above-described method. When performing pass / fail determination, various determination parameters (determination values) can be used. In the present invention, it is possible to perform pass / fail determination based on, for example, the extinction ratio (TM transmittance t _TM ) / (TE transmittance t _TE ).
Here, in the non-defective product determination, it is basically necessary to set a reference value that can be determined as a good product in advance, and to compare this reference value with the value (determination value) of the inspection target portion (measurement point) of the mixed filter 10. is there. For example, the boundary between the X-direction wire grid and the Y-direction wire grid does not function as a wire grid. For this reason, if light is incident on the boundary between the X-direction wire grid and the Y-direction wire grid, the transmittance tends to decrease, so that comparison with the theoretical value cannot be performed.
For example, when quality determination is performed based on the extinction ratio, a portion of the mixed filter 10 that has been determined to be non-defective in advance is used as a reference point, and the extinction ratio at the reference point is set as a reference value. The quality is determined by comparing this reference value with the extinction ratio (determination value) at the measurement point.

The reference point may be a measurement point at which fine measurement is performed in advance with respect to the line width, presence / absence of defects, or the like by observation with an electron beam microscope or the like. Alternatively, instead of the reference point, a reference value reflecting a tendency regarding the line width and pitch of the mixed filter may be set with reference to a value obtained by simulation or the like. When the difference between the judgment value and the reference value is within a predetermined allowable value, the measurement point part of the mixed type filter to be inspected is determined to be non-defective, and when it is not within the allowable value, the mixed type to be inspected The measurement point portion of the filter is determined to be defective. As described above, the quality comparison of the mixed filter to be inspected can be performed by comparing the data of the reference value and the determination value.
In addition, in the quality determination using the above extinction ratio, by performing measurement while changing the measurement point of the mixed filter to be inspected, it is possible to identify a “defective portion” having a low polarization selection performance in the mixed filter. Can do. In addition, the TM transmittance of the X-direction wire grid or the TM transmittance of the Y-direction wire grid may be used for the quality determination.

[Inspection equipment]
An inspection apparatus for inspecting a mixed filter based on the above principle will be described with reference to FIG. FIG. 3 is a schematic configuration diagram of an inspection apparatus according to an embodiment of the present invention.
The inspection apparatus 100 generally includes an optical system 110 and a processing apparatus 130.
The optical system 110 includes a light source 111 of inspection light that irradiates the measurement target S (mixed filter), a beam expander 113 (light intensity averaging means) that makes the light intensity of the inspection light emitted from the light source 111 uniform. , The inspection light that has passed through the beam expander 113 is spotted to irradiate the measuring object S, and the polarizer 117 that transmits a predetermined polarization component of the inspection light transmitted through the pinhole (polarization for inspection) A polarizer 117, a polarizer rotator 119 (inspection polarizer rotator) that supports the polarizer 117 so that the angle of the transmission axis thereof can be adjusted, and a rotating device drive unit 119 a (rotation drive unit 119 a ( Rotation drive means), an XY stage 121 that movably supports the measuring object S, and a stage drive that independently drives the XY stage 121 in the X-axis and Y-axis directions. 121a (stage driving means) and the analyzer 123 (inspection polarizer) that transmits a predetermined polarization component of the inspection light transmitted through the measuring object S and the angle of the transmission axis of the analyzer 123 can be adjusted. The analyzer rotating device 125 (inspection polarizer holding means) supported on the rotating device 125, the rotating device driving unit 125 a (rotating driving means) for rotating the analyzer rotating device 125, and the inspection light transmitted through the analyzer 123 are detected. And a detector 127 (transmitted light intensity detecting means).

As the light source 111, it is desirable to use a laser or an LED. Since both the laser and the LED have good directivity, the measurement accuracy can be increased.
In addition, the use of a light source that irradiates inspection light having a single wavelength such as a laser can irradiate light with high intensity, and an effect that the transmittance can be easily evaluated can be obtained. When a laser is used, inspection may be performed by selecting a specific wavelength such as a wavelength of 660 nm (red), a wavelength of 532 nm (green), or a wavelength of 780 nm (near infrared). Moreover, you may make it irradiate the measuring object S with the light of a specific wavelength using a white light source and a spectroscope. In any case, it is possible to perform an evaluation focusing on optical characteristics at a specific wavelength of the mixed filter.
The inspection light emitted from the light source 111 is such that the light intensity detected by the detector 127 is substantially the same when the transmission axis of the analyzer 123 is 0 ° and when it is 90 °. In other words, it is preferably non-polarized light. When a semiconductor laser is used as the light source 111, the emitted light tends to have a high light intensity in a direction perpendicular to the light emitting layer, and thus there is a problem that the light intensity is not constant depending on the incident angle. Therefore, when a semiconductor laser is used as the light source 111, the inspection light is incident on the surface of the measuring object S and the analyzer 123 with an inclination of about 45 ° so that the light intensity becomes uniform. Is preferred. Note that when a non-polarized white light source, a laser, or an LED is used as the light source 111, the above matters do not matter.

The beam expander 113 is disposed between the light source 111 and the measurement target S. The beam expander 113 equalizes the light intensity of the inspection light from the light source 111 within the irradiation range so that the inspection light with a uniform intensity is irradiated onto the measurement point of the measurement target S. adjust. By making the light intensity uniform by the beam expander 113, the measurement accuracy of the transmittance can be improved.
The pinhole 115 reduces the diameter of the inspection light to a predetermined dimension. The diameter of the spot light formed by the pinhole 115 is set to be sufficiently larger than one side of the unit region where each wire grid of the mixed filter that is the measurement target S is formed. Therefore, since a sufficient number of unit regions are included in the spot irradiation range, the area ratio of the X-direction wire grid and the Y-direction wire grid included in the spot irradiation range is a mixed type as the measurement target S. The area ratio of the X-direction wire grid and the Y-direction wire grid of the filter is substantially equal.

The polarizer 117 is a polarization filter that transmits a predetermined polarization component of the inspection light. The angle of the transmission axis of the polarizer 117 is rotated from 0 ° to 180 ° by a predetermined angle (for example, every 15 °) by the polarizer rotating device 119. The rotation device drive unit 119a that rotates the polarizer rotation device 119 is driven and controlled by a control unit 131 in the processing device 130 described later.
The XY stage 121 moves the measurement target S so that the inspection light is irradiated to a desired measurement point of the measurement target S. The stage drive unit 121a that drives the XY stage 121 is driven and controlled by a control unit 131 in the processing apparatus 130 described later.
The analyzer 123 is a polarization filter that transmits a predetermined polarization component of the inspection light. The angle of the transmission axis of the analyzer 123 is adjusted by the analyzer rotating device 125 so that, for example, 0 ° polarized light (first polarized component), 45 ° polarized light, or 90 ° polarized light (second polarized component) is transmitted. Is done. The analyzer rotating device 125 adjusts and holds the analyzer 123 at a predetermined transmission axis angle. The rotation device driving unit 125a that rotationally drives the analyzer rotation device 125 is driven and controlled by a control unit 131 in the processing device 130 described later.
The detector 127 (first detection means, second detection means) is a well-known light detection device having a photodiode. The detector 127 detects the intensity of the inspection light transmitted through the analyzer 123 and outputs an analog light intensity signal to the control unit 131 in the processing apparatus 130 at the subsequent stage.

The processing device 130 includes a control unit 131 (transmittance calculation means, pass / fail judgment means) that executes various arithmetic processes, calculation of optical characteristics of the measurement target S, or calculation programs and various data necessary for the pass / fail judgment. A storage unit 133 for storing, a display unit 135 for displaying determination results, setting contents, and the like, and an input unit including a keyboard 137 and a mouse 139 for inputting setting contents are provided.
The control unit 131 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like.
The ROM stores a startup program for the processing device 130 and the like. In the RAM, a program stored in the ROM or the storage unit 133 is booted, and when the program is started, the RAM becomes a work area where the CPU reads and writes. The CPU boots programs in the ROM and the storage unit 133 to the RAM, and executes each program while using the RAM as a work memory.
The storage unit 133 includes an HDD (Hard Disk Drive) and the like. The storage unit 133 stores a control program for controlling the stage drive unit 121a and the rotating device drive unit 125a, a program related to a calculation process of transmittance and extinction ratio, a measurement result of each measurement point of the measurement target S, and the like. Remembered.
The keyboard 137 and the mouse 139 are means for inputting tolerance values for determining whether the measuring object S is acceptable, the coordinate axes of the measuring points of the measuring object, and the like. The input tolerance value is stored in the RAM.

[Optical characteristics calculation flow]
FIG. 4 is a flowchart showing a method for calculating the optical characteristics of the optical element performed by the inspection apparatus. In addition, the quality determination based on the calculated optical characteristic is performed in step S21. Further, the calculation of the optical characteristics for the portion (reference point) of the mixed filter 10 that has been determined to be non-defective in advance is also performed according to this flow. In this case, the process is terminated without performing the pass / fail determination for the reference point, or the process of the next step (step S23 and subsequent steps) is performed to perform the pass / fail determination at the measurement points other than the reference point.

In step S1, the control unit 131 controls the stage driving unit 121a so as to move the XY stage 121 to the initial position. Here, the initial position is a position where the first measurement point of the mixed filter 10 that is the measurement target S is irradiated with the inspection light.
In step S3, the control unit 131 controls the rotation device driving unit 125a so that the analyzer 123 transmits 0 ° polarized light. That is, the control unit 131 adjusts the angle of the transmission axis of the analyzer 123 by controlling the rotation device driving unit 125a.
In step S5, the control unit 131 controls the rotation device driving unit 119a so that the polarizer 117 transmits 0 ° polarized light. That is, the control unit 131 adjusts the angle of the transmission axis of the polarizer 117 by controlling the rotation device driving unit 119a.

In step S7, the control unit 131 controls the light source 111 so that the light source 111 emits inspection light. The inspection light emitted from the light source 111 enters the beam expander 113 and the light intensity is made uniform. The inspection light having the uniform light intensity enters the pinhole 115 and is converted into spot light having a predetermined diameter. The inspection light converted into the spot shape is incident on the polarizer 117. The polarizer 117 transmits only a predetermined polarization component of the inspection light. The light passes through the polarizer 117 and is irradiated to a predetermined measurement point of the measurement object S. This inspection light is sufficiently larger than the unit area of the X-direction wire grid and Y-direction wire grid of the mixed filter included in the measurement point, and the X-direction wire grid and Y-direction wire included in the irradiation area of the inspection light. The area ratio of the grid is equal to the area ratio of the X-direction wire grid and the Y-direction wire grid of the mixed filter. The inspection light that has passed through the measuring object S enters the analyzer 123. The analyzer 123 transmits only a predetermined polarization component of the inspection light. The inspection light that has passed through the analyzer 123 enters the detector 127. The detector 127 detects the intensity of the inspection light and outputs an analog light intensity signal.
In step S9, the control unit 131 converts the analog light intensity signal output from the detector 127 into digital data using a sampling clock having a predetermined frequency in the A / D converter 131a, and acquires light intensity data. . The control unit 131 stores the acquired intensity data in the storage unit 133.

In step S11, the control unit 131 confirms whether or not the angle of the transmission axis of the polarizer 117 is 180 °. The reason why the angle is set to 180 ° is to acquire transmitted light intensity data for at least one cycle of the sine curve related to the intensity I of the inspection light. If the angle of the transmission axis of the polarizer 117 is not 180 ° (No in step S11), acquisition of data for one cycle of transmitted light intensity is completed in a state where the analyzer 123 is set to a predetermined angle. If not. In this case, the process proceeds to step S13, and the control unit 131 controls the rotation device driving unit 119a to rotate the angle of the transmission axis of the polarizer 117 by 15 °. That is, the control unit 131 adjusts the angle of the transmission axis of the polarizer 117 by controlling the rotation device driving unit 119a. The rotation angle of 15 ° here is an example, and the rotation angle can be set to an arbitrary angle. Thereafter, the processing from step S9 is performed.
In step S11, when the angle of the transmission axis of the polarizer 117 is 180 ° (Yes in step S11), the data of one cycle of the transmitted light intensity is obtained with the analyzer 123 set to a predetermined angle. This is when acquisition is completed. In this case, the control unit 131 performs the process of the next step S15.

In step S15, the control unit 131 confirms whether or not the angle of the transmission axis of the analyzer 123 is 90 °. When the angle of the transmission axis of the analyzer 123 is not 90 ° (No in step S15), the transmission light intensity data acquisition at the measurement point of the mixed filter 10 is not completed. In this case, the process proceeds to step S17, and the control unit 131 controls the rotation device driving unit 125a to rotate the angle of the transmission axis of the analyzer 123 by 45 °. That is, the control unit 131 adjusts the angle of the transmission axis of the analyzer 123 by controlling the rotation device driving unit 125a. And the process below step S5 is performed.
In step S15, when the angle of the transmission axis of the analyzer 123 is 90 ° (Yes in step S15), acquisition of transmitted light intensity data at the measurement point of the mixed filter 10 is completed. In this case, the process proceeds to step S19, and the control unit 131 controls the light source 111 so that the light source 111 stops emission of the inspection light.

In step S21, the control unit 131 calculates the optical characteristics of the measurement target S. That is, the control unit 131 (transmittance calculating means) reads transmitted light intensity data with the transmission axis angle of the analyzer 123 being 0 ° from the storage unit 133 and calculates the TM transmittance t _TM1 of the X-direction wire grid 11x. . Further, the control unit 131 reads transmitted light intensity data when the transmission axis angle of the analyzer 123 is 45 ° from the storage unit 133, and the TM transmittance t _TM as the entire measurement target S (mixed filter 10), TE transmittance t _TE and extinction ratio t _TM / t _TE are calculated. Further, the control unit 131 reads transmitted light intensity data when the transmission axis angle of the analyzer 123 is 90 ° from the storage unit 133 and calculates the TM transmittance t _TM2 of the Y-direction wire grid 11y. Finally, the control unit 131 sets the calculated TM transmittance t _TM1 , TM transmittance t _TM2 , TM transmittance t _TM , TE transmittance t _TE , and extinction ratio t _TM / t _TE to the coordinate axis of the XY stage 121, in other words, Labeling is performed together with the position coordinates of the measurement point and stored in the storage unit 133.

Moreover, you may perform quality determination of a measurement point site | part in step S21. That is, in step S21, the control unit 131 (good / bad determining means) compares the extinction ratio t _TM / t _TE (determination value) calculated in step S21 with the reference value of the extinction ratio t _TM / t _TE. Make a decision. The control unit 131 reads from the storage unit 133 the extinction ratio t _TM / t _TE (reference value) at the reference point of the mixed filter that is determined as a good product in advance. An absolute value of a value obtained by subtracting a predetermined reference value of the extinction ratio from the extinction ratio t _TM / t _TE (determination value) calculated in step S21 is calculated. When this absolute value is within a predetermined tolerance range, it is determined that the measurement point is a non-defective part having good optical characteristics, and when the absolute value is outside the tolerance range, The measurement point is determined to be a defective part that does not have good optical characteristics. The control unit 131 labels the pass / fail judgment result together with the coordinate axis of the XY stage 121, in other words, the position coordinate of the measurement point, and stores the result in the storage unit 133.
This allowable value is determined according to the yield of the product and the performance of the product to be finally obtained. If the allowable value is set to be small, that is, the difference from the reference point is set to be small, only a high-performance mixed filter can be selected, but the product yield is reduced. On the contrary, if the allowable value is increased, the product yield will be improved.

In step S <b> 23, the control unit 131 confirms whether the optical characteristics have been calculated at all measurement points of the measurement target S. If the calculation of the optical characteristics of all the measurement points has been completed (Yes in step S23), the process ends. If there are remaining measurement points for which optical characteristics should be calculated (No in step S23), the process proceeds to step S25.
In step S25, the control unit 131 controls the stage driving unit 121a so as to move the XY stage 121 to a position where the inspection light is irradiated to the next measurement point to be measured.
And the process after step S3 is repeated.

Embodiment 1
FIGS. 5A and 5B are schematic views showing an example of an optical element that can be an inspection object in the present invention. The mixed filter to be inspected in the first embodiment is a mixed filter 10A in which an X-direction wire grid 11x and a Y-direction wire grid 11y are arranged in a checkered pattern as shown in FIG. The area ratio A: B of the wire grid between the direction and the Y direction is 1: 1. This mixed filter 10A is a mixture of an X-direction wire grid and a Y-direction wire grid formed of aluminum (Al) on a quartz substrate (4 inch wafer, thickness: 1 mm).
In the present invention, an optical element as shown in FIG. The mixed filter 10B shown in FIG. 5B is an optical element in which a plurality of parallelogram shaped unit regions 11 are arranged in parallel. In the mixed filter 10B, the X-direction wire grid 11x and the Y-direction wire grid 11y are alternately arranged at an area ratio of 1: 1. As described above, the mixed filter 10 in which the X-direction wire grid 11x and the Y-direction wire grid 11y are arranged at an area ratio of 1: 1 can be an inspection target according to the present invention.

  In the first embodiment, a semiconductor laser (wavelength 550 nm) is used as the light source 111 of the inspection apparatus 100 (see FIG. 3). The pinhole 115 had a diameter of about 2 mm, and the surface of the mixed filter 10A was irradiated with spot-shaped inspection light having a diameter of about 2 mm. The spot diameter of the inspection light applied to the mixed filter 10 is set to be sufficiently larger than one side of the unit region 11. That is, the area ratio of the X-direction wire grid 11x and the Y-direction wire grid 11y included in the spot light irradiation range is the area of the X-direction wire grid 11x and the Y-direction wire grid 11y of the mixed filter 10 as the measurement target S. It is set to be approximately equal to the ratio.

  6 to 8 show examples of the measurement results of the transmittance of the mixed filter 10A shown in FIG. In FIG. 6, the angle of the transmission axis of the analyzer 123 (see FIG. 3) is set to 0 ° (0 ° polarization component is transmitted), and the angle of the transmission axis of the polarizer 117 is changed from 0 ° to 180 °. It is the graph which showed the change of the transmittance | permeability in the case of. In FIG. 7, the angle of the transmission axis of the analyzer 123 is set to 45 ° (an intermediate angle between the X-direction wire grid and the Y-direction wire grid, and the 45 ° polarization component is transmitted), and the analyzer 123 (FIG. 3) is set. Graph) showing the change in transmittance when the angle of the transmission axis is set to 0 ° (0 ° polarization component is transmitted) and the angle of the transmission axis of the polarizer 117 is changed from 0 ° to 180 °. FIG. In FIG. 8, the angle of the transmission axis of the analyzer 123 (see FIG. 3) is set to 90 ° (90 ° polarization component is transmitted), and the angle of the transmission axis of the polarizer 117 is changed from 0 ° to 180 °. It is the graph which showed the change of the transmittance | permeability in the case of.

In FIG. 6, since the angle of the transmission axis of the analyzer 123 is 0 °, the polarization component of 0 ° is transmitted when the angle of the transmission axis of the polarizer 117 is also 0 °. Therefore, it can be said that the transmittance when the angles of the transmission axes of the analyzer 123 and the polarizer 117 are both 0 ° indicates the transmission function of the X-direction wire grid 11x of the mixed filter 10A to be inspected. As described above, the TM transmittance t _TM1 of the X-direction wire grid 11x may be obtained by measuring only the transmittance when the angle of the transmission axis of the polarizer 117 is 0 °.

In FIG. 8, since the angle of the transmission axis of the analyzer 123 is 90 °, the polarization component of 90 ° is transmitted when the angle of the transmission axis of the polarizer 117 is also 90 °. Therefore, it can be said that the transmittance when the angles of the transmission axes of the analyzer 123 and the polarizer 117 are both 90 ° indicates the transmission function of the Y-direction wire grid 11y of the mixed filter 10A to be inspected. As described above, the TM transmittance t _TM2 of the Y-direction wire grid 11y may be obtained by measuring only the transmittance when the angle of the transmission axis of the polarizer 117 is 90 °.

FIG. 7 shows the dependency of the transmittance on the transmission axis angle of the polarizer 117 (polarizer transmission axis angle dependency) when the angle of the transmission axis of the analyzer 123 is 45 °. From this measurement result, the TM transmittance t _TM and the TE transmittance t _TE of the entire mixed filter 10A can be calculated by performing the above-described calculation. Specifically, X and Y were obtained by fitting to the curve “X + Ysin2φ” (formula (4)) from the graph of the measurement results using the least square method or the like. TM transmittance t _TM and TE transmittance t _TE were calculated by solving simultaneous equations (formula (5)) from the obtained X and Y. As a result, TM transmittance t _TM was 83% and TE transmittance t _TE. Was determined to be 2.5%. This value is calculated under the assumption that the production accuracy of the X-direction wire grid 11x and the Y-direction wire grid 11y of the mixed filter 10A is the same.
By calculating without using the above assumptions and approximations, TM transmittance t _TM1 and TE transmittance t _TE1 of the X-direction wire grid 11x, TM transmittance t _TM2 and TE transmittance t of the Y-direction wire grid 11y are obtained. It is also possible to obtain _TE2 individually.

  The angle (0 °, 45 °, 90 °, etc.) of the transmission axis of the analyzer shown in this embodiment is not an absolute angle, but is determined based on the angle of the wire grid of the mixed filter to be measured. Relative angle. That is, 0 ° and 90 ° are angles corresponding to the angles of the transmission axes of the X-direction wire grid and the Y-direction wire grid, respectively. Further, 45 ° is an angle just between the transmission axes of the X-direction wire grid and the Y-direction wire grid. In other words, 45 ° is an angle obtained by rotating the transmission axis of the X-direction wire grid and the Y-direction wire grid by 45 ° in the plus or minus direction with respect to the transmission axis.

Further, in the present embodiment, the measurement example in which the angle of the transmission axis of the analyzer 123 is set to 0 °, 45 °, and 90 ° is shown, but there is no problem even if the angle is 90 °, 135 °, and 180 °.
Further, the angle of the transmission axis of the analyzer 123 may be set to 45 °, 90 °, and 135 °. In this case, the TM transmittance is calculated around the Y-direction wire grid, and the TM transmittance of the X-direction wire grid is calculated based on the assumption that the X-direction wire grid creation accuracy is the same as that of the Y-direction wire grid. become. In addition, since the measurement at the intermediate angle between the X-direction wire grid 11x and the Y-direction wire grid 11y is performed twice (measurement when the angle of the transmission axis of the analyzer 123 is 45 ° and 135 °), the wire grid An error (relative angle) generated between the angle of the transmission axis and the angle of the transmission axis of the polarizer can be corrected, and the measurement accuracy can be improved.

Of course, the TM transmittance and the TE transmittance t _TE may be calculated only from the measurement in which the angle of the transmission axis of the analyzer 123 is set to 45 °.
Furthermore, the measurement is performed with the angle of the transmission axis of the analyzer 123 set to the angle of one transmission axis of the X-direction wire grid and the Y-direction wire grid, and the TM transmittance of each wire grid is calculated. It is also possible to calculate the TM transmittance, the TE transmittance, and the extinction ratio as a whole of the optical element by performing measurement by shifting the angle of the transmission axis of 45 °.
In any case, the measurement may be performed from any angle.

  As described above, according to the present embodiment, with respect to the mixed filter 10 in which the X-direction wire grid 11x and the Y-direction wire grid 11y are arranged at a ratio of 1: 1, the X-direction wire grid and the Y-direction wire. The TM transmittance of the grid can be calculated at high speed without contact, and the TM transmittance, TE transmittance, and extinction ratio of the entire optical element can be calculated.

[Embodiment 2]
Unlike the first embodiment, the present embodiment is characterized in that an LED is used as the light source 111 of the inspection apparatus 100 (see FIG. 3). Even when the LED light source is used, the optical characteristics of the mixed filter at a specific wavelength can be examined as in the case where the laser light source is used. In addition, since the LED has sufficient light intensity, it is possible to measure with high accuracy.
Furthermore, by using an LED as the light source 111, it is possible to investigate whether or not the optical characteristics of the mixed filter, more specifically, the optical characteristics of the wire grid constituting the mixed filter are suitable for projector use.
In other words, projectors are used not only as polarizing beam splitters and analyzers, but also as reflective polarizers for polarization reuse. When a polarizer is used in a projector, the polarizer has an RGB wavelength. In some cases, different polarizers are used so as to exhibit good polarization characteristics (optical characteristics). Therefore, if the optical characteristics of the mixed filter can be measured for each wavelength of RGB using LEDs corresponding to the RGB wavelengths, it can be determined whether or not the mixed filter is suitable for the projector.

[Embodiment 3]
This embodiment is characterized in that the mixed filter to be inspected is a one-dimensional photonic crystal element using a multilayer film. Note that the arrangement of the X-direction wire grid and the Y-direction wire grid of the mixed filter and the measurement apparatus used for the inspection are the same as those in the first embodiment, and thus description thereof is omitted.
The sample to be inspected is formed with a multilayer film in which Ta ₂ O ₅ (tantalum pentoxide) and SiO ₂ (silicon dioxide) are alternately laminated. Note that Ta ₂ O ₅ functions as a high refractive index material, and SiO ₂ functions as a low refractive material.
Such a mixed filter can be formed by preparing a line pattern in advance on the surface of a quartz substrate and then alternately depositing Ta ₂ O ₅ and SiO ₂ by a vacuum film forming method. That is, by appropriately changing the direction of the line pattern on the quartz substrate surface for each reference region, the first polarizing region that transmits the X-polarized component and the second polarizing region that transmits the Y-polarized component in a predetermined pattern. Two-dimensional arrangement is possible.

With respect to the specimen to be inspected as described above, if the inspection apparatus according to one embodiment of the present invention is used, the optical characteristics of the mixed filter can be calculated as in the above embodiments.
In addition to this, as the mixed filter, for example, a polarizer including silver ellipsoidal particles in borosilicate glass can be an inspection object. Further, the substrate of the optical element is not limited to a glass substrate such as a quartz substrate, a borosilicate glass substrate, or BK7, but may be a transparent resin film.

[Embodiment 4]
FIG. 9 is a schematic diagram of an optical element to be inspected in the fourth embodiment.
A plurality of chips 15 are formed on the 4-inch wafer 13 shown in FIG. The chip 15 is a 3 mm square chip. A plurality of micron-order unit regions 11 are formed on the chip 15, and an X-direction wire grid 11 x or a Y-direction wire grid 11 y is formed in each unit region 11. That is, the chip 15 is substantially the same as the mixed filter 10 described above. The chip 15 is a mixed filter in which the X-direction wire grid 11x and the Y-direction wire grid 11y are arranged in a checkered pattern, and the area ratio A: B of the wire grid between the X direction and the Y direction is 1: 1. It is.

In the present embodiment, the wafer 13 is placed on the XY stage 121 as the measurement target S shown in FIG. In addition, since the inspection apparatus 100 used for the inspection is the same as that of the first embodiment, the description thereof is omitted.
When performing the pass / fail determination, the stage drive unit 121a was controlled by the stage drive unit of the control unit 131 so that the inspection light was irradiated to the center of each chip 15.
The pass / fail judgment was performed as follows. That is, first, a reference value that can be determined as a non-defective product was prepared in advance. Then, the inspection device 100 measures the transmitted light intensity of each chip 15 with the transmission axis angle of the analyzer 123 set to 45 °, and calculates the TM transmittance t _TM and the TE transmittance t _TE . . The extinction ratio as a judgment value was determined from the calculated TM transmittance t _TM and TE transmittance t _TE . The absolute value of a value obtained by subtracting the reference value was calculated from the obtained determination value. When this absolute value is within a predetermined tolerance range, it is determined that the measurement point is a non-defective part having good optical characteristics, and when the absolute value is outside the tolerance range, The measurement point was determined to be a defective part that did not have good optical characteristics.
In the present embodiment, as a result of the above quality determination, it was possible to determine 35 good products and 1 defective product from the 36 chips 15.

  DESCRIPTION OF SYMBOLS 10, 10A, 10B ... Mixed filter, 11 ... Unit region, 11x ... X direction wire grid, 11y ... Y direction wire grid, 13 ... Wafer, 15 ... Chip, 100 ... Inspection apparatus, 110 ... Optical system, 111 ... Light source , 113 ... Beam expander, 115 ... Pinhole, 117 ... Polarizer, 119 ... Polarizer rotation device, 119a ... Rotation device drive unit, 121 ... XY stage, 121a ... Stage drive unit, 123 ... Analyzer, 125 ... Detection Photon rotating device, 125a ... rotating device driving unit, 127 ... detector, 130 ... processing device, 131 ... control unit, 131a ... A / D converter, 133 ... storage unit, 135 ... display unit, 137 ... keyboard, 139 ... Mouse, S ... Measurement target

JP 2007-315990 A

Claims (7)

A first polarization region that transmits a first polarization component of incident light and a second polarization region that transmits a second polarization component orthogonal to the first polarization component of incident light are two-dimensionally arranged. An inspection apparatus for optical elements,
A light source for irradiating inspection light to a region sufficiently larger than the first polarizing region and the second polarizing region of the optical element;
Two inspection polarizers that are respectively disposed in a front stage and a rear stage of the optical element and transmit a predetermined polarization component of the inspection light;
Of the two inspection polarizers, the one inspection polarizer is adjusted so that the transmission axis of one inspection polarizer is an angle rotated by 45 degrees from the angle of the transmission axis of the first polarization region. Holding inspection polarizer holding means;
Inspection polarizer rotating means for rotating the transmission axis of the other inspection polarizer among the two inspection polarizers by a predetermined angle;
Transmitted light intensity detecting means for detecting transmitted light intensity of the inspection light transmitted through the two inspection polarizers and the optical element;
The inspection light transmitted through the other inspection polarizer rotated by a predetermined angle by the inspection polarizer rotating means is detected by the transmitted light intensity detection means, and transmitted at the detected predetermined angles. An inspection device for an optical element, comprising: transmittance calculating means for calculating TM transmittance and TE transmittance of the optical element based on light intensity.   The transmittance calculating means utilizes the fact that the TM transmittance and the TE transmittance of each of the first polarizing regions and the second polarizing regions coincide with each other, so that the TM transmittance and the TE transmittance of the optical element are matched. The optical element inspection apparatus according to claim 1, wherein the ratio is calculated. The inspection polarizer holding means is configured such that the transmission axis of the one inspection polarizer matches the angle of the transmission axis of the first polarization region or the second polarization region. Holding a child,
The inspection polarizer rotating means moves the other inspection polarizer so that the angle of the transmission axis of the other inspection polarizer matches at least the angle of the transmission axis of the one inspection polarizer. Hold and
The transmittance calculating means calculates the TM transmittance of the first polarizing region and / or the second polarizing region from the transmitted light intensity of the inspection light detected by the transmitted light intensity detecting means. The optical element inspection apparatus according to claim 1, wherein the optical element inspection apparatus is an optical element inspection apparatus.   The optical element according to any one of claims 1 to 3, further comprising light intensity averaging means for making the light intensity of the inspection light uniform in an irradiation region in a front stage of the optical element. Inspection device.   5. The optical element inspection apparatus according to claim 1, wherein the light source is a light source that emits inspection light having a single wavelength. 6.   When the absolute value of a value obtained by subtracting a predetermined reference value from the determination value obtained from the TM transmittance and the TE transmittance calculated by the transmittance calculating means is within a predetermined range, the optical element is a non-defective product. The optical element inspection apparatus according to claim 1, further comprising: a quality determination unit that determines that A first polarization region that transmits a first polarization component of incident light and a second polarization region that transmits a second polarization component orthogonal to the first polarization component of incident light are two-dimensionally arranged. An inspection method for an optical element, comprising:
With respect to one inspection polarizer set at the front stage or the rear stage of the optical element and set to the transmission axis angle rotated by 45 degrees with respect to the transmission axis angle of the first polarizing region, the front stage of the optical element Alternatively, an inspection polarizer rotating step of rotating the other inspection polarizer arranged at the other end of the latter stage by a predetermined angle;
The optical element is irradiated with inspection light having an irradiation area sufficiently larger than the first polarizing area and the second polarizing area, and the optical element, the one inspection polarizer, and the inspection polarizer rotation are irradiated. A transmitted light intensity detecting step for detecting the transmitted light intensity of the inspection light transmitted through the other inspection polarizer rotated at a predetermined angle in the process at each predetermined angle;
A transmittance calculating step of calculating a TM transmittance and a TE transmittance of the optical element based on the transmitted light intensity at each predetermined angle detected in the transmitted light intensity detecting step. Inspection method for optical elements.

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